Dashevskaya E I, Litvin I, Nikitin E E, Troe J
Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel.
Phys Chem Chem Phys. 2007 Apr 7;9(13):1559-67. doi: 10.1039/b615826a. Epub 2007 Feb 2.
The low-energy capture of dipolar diatomic molecules in an open electronic state by ions is usually considered to be induced by the first-order charge-permanent dipole interaction with other terms of the long-range potential playing a minor role. If the molecular dipole moment is anomalously small (as is the case for slightly asymmetrical molecules), however, the situation changes, and the capture dynamics is strongly affected by higher orders of the charge-permanent dipole, charge-permanent quadrupole, and charge-induced dipole interactions. The interplay of different terms in the interaction potential manifests itself in complicated temperature dependence of the rotationally state-specific capture rate coefficients. These features of the capture are studied by way of example for NO(X (2)Pi(1/2), j) + C(+) collisions in the temperature range 10(-2)-20 K where the dynamics is adiabatic with respect to rotational and fine-structure transitions and sudden with respect to transitions between Lambda doubling and hyperfine states. The theoretical rate coefficient, which depends on the translational and rotational temperature, agrees with the experimental one measured at T(tr) = 0.6 K and T(rot) = 20 K.
离子对处于开放电子态的偶极双原子分子的低能俘获通常被认为是由一阶电荷 - 永久偶极相互作用引起的，而长程势的其他项起次要作用。然而，如果分子偶极矩异常小（对于略微不对称的分子就是这种情况），情况就会改变，俘获动力学将受到电荷 - 永久偶极、电荷 - 永久四极和电荷 - 诱导偶极相互作用的高阶项的强烈影响。相互作用势中不同项的相互作用表现为特定转动状态俘获速率系数的复杂温度依赖性。通过研究NO(X (2)Pi(1/2), j) + C(+)在10^(-2) - 20 K温度范围内的碰撞实例来探讨俘获的这些特征，其中动力学对于转动和精细结构跃迁是绝热的，而对于Λ双重态和超精细态之间的跃迁是突然的。取决于平动和转动温度的理论速率系数与在T(tr) = 0.6 K和T(rot) = 20 K时测量的实验值相符。
